Material for flexible medical products

ABSTRACT

Improved flexible film and tubing for medical products manufactured from a PVC compound, comprising an amount of ultra high molecular weight (UHMW) PVC resin having an inherent viscosity ranging from about 1.25 to about 2.00, most preferably about 1.71, and about 43 to about 57 percent by weight of a medically acceptable plasticizer, most preferably about 53 percent, such as tri (2-ethylhexyl) trimellitate (TOTM).

TECHNICAL FIELD

The present invention generally relates to novel materials formanufacturing flexible medical products. The invention particularlyrelates to a novel PVC compound that may be used to manufacture plasticfilm and tubing used to make a variety of blood bags.

BACKGROUND OF THE INVENTION

Flexible plastic blood bags first replaced glass bottles for collectingblood as early as the late 1940's. Although blood bags have beenmanufactured from a variety of plastics materials and films, by 1955,the preferred material used for manufacturing flexible plastic bloodbags was polyvinyl chloride (PVC) mixed with a plasticizer.

PVC is a polymerized form of the monomer vinyl chloride. Since polymersgenerally are of little value alone, they must be compounded withvarious additives to make useful material, or plastic. This particularlyis true of PVC plastic. Alone, PVC is a hard and rigid substance andcannot be used to make articles, particularly not blood bag film. PVCmust be plasticized with any one of several plasticizers to provideflexibility. In addition, PVC is heat-sensitive, thus a stabilizer mustbe added to prevent degradation of the polymer at the high temperaturesrequired to melt the polymer and form the desired article, such as afilm or tubing.

There are several classes of polymeric materials currently available inaddition to PVC, including polyethylene, poly(vinylidene chloride),polycaprolactam, and polyisoprene. Each class includes hundreds ofdifferent compounds, making thousands of plastics available for use inmanufacturing various articles. However, the use of these othermaterials for manufacturing certain medical articles, such as bloodbags, which come in direct contact with body fluids and the like thatare reintroduced into the body, is limited by medical and regulatoryrequirements. PVC has the desired properties for manufacturing film ofthe type that is used to produce blood bags.

Specifically, the plastic film must be flexible to permit not onlyfilling during blood collection, but also to permit transfer of theblood components by expression and complete emptying by transfusion.Flexible, pliable material also facilitates centrifugation to separateout the various blood components if desired. The film must be capable ofwithstanding both extremely high temperatures (e.g., 115° C.-120° C.)and extremely low temperatures (e.g., -70° C.), since blood bags must beautoclaved (i.e., sterilized using high-pressure steam), and may besubject to freeze-fracturing to remove blood components.

In addition to use considerations, plastic film used for manufacturingmedical articles, such as blood bags, must satisfy certain constraintsimposed by the manufacturing process. Manufacturing closed containersfrom plastic film, such as blood bags, requires that certain edges holda seal that can withstand the rigors of handling discussed above.Methods for sealing include heat sealing, radio-frequency (RF) sealing,and chemical bonding, among others. RF sealing is preferred for bloodbags, but requires that the plastic material have a certain degree ofpolarity.

As mentioned above, PVC must include a plasticizer to give the otherwiserigid material the desired qualifies, including flexibility. Almostsince its discovery as a viable polymer for use in manufacturing medicalarticles, the plasticizer of choice for PVC blood bags has been di(2-ethylhexyl) phthalate (DEHP). Other well-known medically acceptableplasticizer materials include tri (2-ethylhexyl) trimellitate (TOTM)and, more recently, citrate esters.

It has been reported by various sources since the early 1970's that DEHPplasticizer is lipophilic and tends to extract into blood componentsstored in blood bags manufactured from PVC/DEHP film. Although U.S. Pat.No. 4,222,379 to Smith described the extraction of DEHP as beneficialfor the long term storage of red blood cells (RBCs), concern has beenexpressed about the potential deleterious effects of using suchextractive plasticizers since, over a period of time, considerableamounts of them can collect in blood and blood components. For example,it has been reported that eluted DEHP inhibits the coagulation abilityof platelets.

The leaching of DEHP from DEHP-plasticized PVC spurred development ofnon-leaching plasticizers. TOTM is one of the most commonly usednon-extracting plasticizers. Its use as a PVC plasticizer in blood bagsis described in detail in U.S. Pat. No. 4,280,497 to Warner et al.

High gas transmission is a desired feature of films from which bloodbags used for storing platelets are manufactured, because gastransmission, particularly oxygen transmission, helps to overcomedeleterious pH changes that naturally occur with blood components storedfor extended periods of time. Warner et al. suggests that the amount ofTOTM plasticizer in the PVC used to make blood bag film should rangefrom about 30 to about 50 weight percent, preferably about 37 weightpercent.

Since TOTM was found to be responsible for higher gas transmission,further attempts were made to increase gas transmission of plastic filmsused in the manufacture of blood bags by increasing TOTM content in theplastic. Currently, such improved commercially available blood bagstypically have about 41 percent by weight TOTM in the PVC film. Amountsof TOTM greater than 41 percent are not adequately absorbed in theexisting resin compounds and the resulting film product is both tackyand unmaleable.

Unfortunately, the upper limit of about 41 percent TOTM limits increasedgas transmission in blood bags manufactured from such plastic film.This, in turn, limits the maximum storage duration of blood components,such as platelets, and the quantities of blood components that may bestored in a plastic blood bag of a given size.

In the years since the work leading to the Warner et al. patent,developments have been made in the art of PVC formulation that haveresulted in a wide variety of medical applications for filmsmanufactured from PVC. For example, one method for increasing gastransmission has been the use of alternate plasticizers, such as thecitrate-based plasticizers disclosed in Canada patent 1,280,248 toMahal. n-butryl tri-n-hexyl citrate (BTHC) now is used in manufacturingplastic films having high gas transmission. However, when used tomanufacture platelet blood bags, the BTHC has higher leaching from thePVC than other plasticizers and, like DEHP, is not considered to besuitable for films used for platelet storage bags because of itscoagulation inhibition effect. There have been reports that plateletsstored for seven days in PVC/BTHC bags contain up to 400 ppm BTHC.

Thus, there remains a need for a plastic compound that has high gastransmission, specifically high oxygen transmission, and that otherwiseis suitable for being formed into rims and tubing to be used in medicaldevices and applications.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided an improvedflexible film and tubing that comprises a PVC compound, comprising anmount of ultra high molecular weight (UHMW) PVC resin having an inherentviscosity (logarithmic viscosity number, as defined by ASTM D-1243)ranging from about 1.25 to about 2.00 and about 43 to about 57 percentby weight of a medically acceptable plasticizer, such as tri(2-ethylhexyl) trimellitate (TOTM).

In a preferred embodiment, the UHMW PVC resin has an inherent viscosityof about 1.71 and contains about 50 weight percent plasticizer mostpreferably about 53 weight percent. The novel film manufactured from thePVC compound may be used to manufacture flexible containers for bloodand blood components having an oxygen transmission that is at least 50%higher than that of prior art containers.

In a preferred embodiment, a plasticizer is chosen that extractsrelatively small mounts of the plasticizer into blood components storedin blood bags manufactured from the UHMW PVC films.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bar graph showing the relative gas transmission of: (i) aprior art standard TOTM plasticized PVC bag of Warner et al. (37%standard PVC resin/TOTM); (ii) the current commercially availableproduct (41% standard PVC resin/TOTM), available from Bayer Corporation,having a slightly elevated amount of plasticizer; and (iii) blood bagsmanufactured from a film embodying the present invention hereindisclosed (53% ultra high molecular weight PVC resin/TOTM).

FIG. 2 illustrates a plan view of a multiple blood bag system whichemploys at least one blood bag manufactured using a PVC film embodyingthe present invention.

FIG. 3 is a partial cut-away plan view of a plastic containermanufactured using a PVC film embodying the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is an improved PVC compound that may be made intoflexible plastic film and tubing used to manufacture medical products.The film and tubing are manufactured from the novel polymer compoundthat includes an ultra high molecular weight polyvinyl chloride (PVC)resin, mixed with an amount of a plasticizer in the range of about 43%to about 57%, which plasticizer does not leach in biologicallysignificant amounts from the polymer film under certain use conditions.

The novel plastic film preferably has the qualities of: (1) flexibility,to permit the film to be formed and sealed in a variety of shapes andproducts, such as containers and tubing used in the medical and relatedindustries; (2) pliability, to enable the products manufactured from thefilm to withstand extreme forces, such as centrifugation, without losingform; (3) resilience to temperature fluctuations, so the film canwithstand both high temperatures during sterilization processes and lowtemperatures during freezing for storage or other processing; and (4)high gas transmission, specifically high oxygen transmission. Inaddition, it is preferable that the plasticizer does not significantlyleach out of the plastic compound, either in film or tubing form, andinto contacting fluids during use.

One standard method of identifying PVC resins in the industry is by themolecular weight of the resin. Another method, and the one commonly usedin PVC polymer chemistry, is by dilute solution viscosity measurements.Essentially, this identification method measures the flow of a dilutesolution of PVC resin and a pure solvent through a viscometer. Theresults may variously be calculated under different conditions ofsolvent concentration and temperature as K value, relative viscosity,intrinsic viscosity, and inherent viscosity. The use of these viscosityreferences under the exact same test conditions, is a useful method ofrelating one polymer to another.

These terms are defined by the American Society of Testing and Materials(ASTM) in ASTM D-1243. Specifically, "relative viscosity" is defined asthe ratio of flow time of a solution of a polymer (0.2±0.002 of polymerin 100 ml solvent) to the flow time of a pure solvent. The InternationalUnion of Pure and Applied Chemistry (IUPAC) term for relative viscosityis "viscosity ratio". "Specific viscosity" is defined as relativeviscosity minus one. Specific viscosity represents the increase inviscosity that may be attributed to the polymeric solute. "Reducedviscosity" is defined as the ratio of specific viscosity to theconcentration. Reduced viscosity is a measure of the specific capacityof the polymer to increase the relative viscosity. "Inherent viscosity"is defined as the ratio of the natural logarithm of the relativeviscosity to the concentration. The IUPAC term for inherent viscosity islogarithmic viscosity number. "Intrinsic viscosity" is defined as thelimit of the reduced and inherent viscosities as the concentration ofthe polymeric solute approaches zero and represents the capacity of thepolymer to increase viscosity. Interactions between solvent and polymermolecules have the affect of yielding different intrinsic viscositiesfor the same polymer in various solvents. The IUPAC term for intrinsicviscosity is limiting viscosity number.

Briefly, the method used to determine dilute solution viscosity involvestaking a sample of resin is dissolved in cyclohexanone to make asolution of specified concentration. Inherent viscosity (logarithmicviscosity number) is calculated from the measured flow times of thesolvent and of the polymer solution. Relative and inherent viscosity(viscosity ratio and logarithmic viscosity number) are calculated basedon the following respective formulae:

    η.sub.re1 =t/t.sub.o                                   (1)

    η.sub.inh =(1n.sub.ηre1)/C                         (2)

wherein:

η_(re1) represents relative viscosity (viscosity ratio), t representsefflux time of the solution, t_(o) represents efflux time of the puresolvent, C represents weight of sample used per 100 milliliter ofsolvent, .sub.ηinh represents inherent viscosity (logarithmic viscositynumber), and 1n.sub.ηre1 represents natural logarithm of relativeviscosity (viscosity ratio). In general, the higher the inherentviscosity, the more plasticizer that can be absorbed by the resinparticles, thereby permitting fabrication of higher plasticizer,increased gas transmission films.

High inherent viscosity PVC resins also are referred to as ultra highmolecular weight (UHMW) PVC resins. Thus, UHMW PVCs may be defined asPVCs having an inherent viscosity above about 1.25, typically as high asabout 2.00.

The plastic used in manufacturing the PVC compound of the presentinvention preferably is an ultra high molecular weight PVC resin. Suchresins are commercially available from Occidental Chemical Corp., VinylsDivision, Dallas, Tex., and have the typical properties set forth inTable 1 below.

                  TABLE I                                                         ______________________________________                                        Property                 Range                                                ______________________________________                                        Inherent Viscosity       1.25-1.71                                            (ASTM D-1243)                                                                 Relative Viscosity       2.80-4.00                                            (1% Solution in Cyclohexane @25° C.)                                   K Value                  78-93                                                (DIN 53726)                                                                   Specific Gravity         1.4                                                  (ASTM D-792)                                                                  Bulk Density (gm/cc)     0.49-0.43                                            (ASTM D-1895)                                                                 Particle Size Distribution:                                                   (ASTM D-1921/OCC Test 510)                                                    % Retained, 40 Mesh      0                                                    % Through, 200 Mesh      10-5                                                 Plasticizer Sorption     110-135                                              (ASTM D-1755)                                                                 Volatiles, %             0.3                                                  (OCC Test 260)                                                                ______________________________________                                    

The UHMW PVC resins of the type described above, have about 0.3%volatiles. The above property values represent approximate values,actual values may fluctuate depending on the particular batchcomposition for each resin.

Using such UHMW PVC resin enables the production of film sheets havingabout 100% improved gas transmission over other plastic films, dependingon the amount and type of plasticizer used and as shown in FIG. 1. Thisis due to an increase in plasticizer absorption by the UHMW PVC, whichenables the production of a PVC formulation containing a plasticizer inan amount above the absorption limitation of standard PVC resins incurrent medical products. Gas transmission may be measured usingconventional means. See, for example, the method described in U.S. Pat.No. 4,280,497 to Warner et al.

Several plasticizers may be used in the present UHMW PVC resincompounds. In addition to TOTM, other candidate plasticizers includedi-(2-ethylhexyl-phthalate (DEHP) and citrate ester plasticizers. Suchcitrate ester plasticizers include: acetyl tri-n-butyl citrate (ATBC);n-butyryl tri-n-hexyl citrate (BTHC); acetyl tri-n-octyl citrate (ATOC);and acetyl tri-n-decyl citrate (ATDC). Secondary plasticizers may beadded to the UHMW PVC resin compound for compound stability. Examples ofsuch stabilizers include epoxized soybean oil (ESO), epoxized linseedoil (ELO), and calcium-zinc stearates, among others.

The TOTM plasticizer extracts, or leaches out of the plastic and intothe blood or blood components stored in a blood bag manufactured fromsuch plastic, at a rate of less than about five parts per million after7 days storage. Thus, TOTM is a preferred plasticizer over most otherplasticizers. By comparison, both DEHP and BTHC plasticizers formulatedin PVC compounds leach out of the plastic at a rate of about 300 to 400parts per million for the same length of storage.

Resins currently commercially available have an absorption limit offorty-one (41%) TOTM, whereas the UHMW PVC resin compound of the presentinvention has an upper absorption limit of about fifty-seven (57%) TOTM.FIG. 1 illustrates the relationship between percentage TOTM and oxygengas transmission. The horizontal axis represents percentage TOTMplasticizer in a PVC plastic film in plastic blood bags used for thecollection, processing, and/or storage of blood or blood components,such as platelets. The vertical axis represents micromoles of oxygen perhour, for a standardized 350 cm² bag in room air at 22° C. Asillustrated in FIG. 1, blood bags manufactured from currently availablestandard resins formulated with 37%-41% TOTM plasticizer have asignificantly lower gas transmission than one manufactured using theUHMW resin formulated with 53% TOTM. Plastic films manufactured inaccordance with the present invention preferably have an oxygentransmission rate of greater than about 18 micromoles oxygen per hour asmeasured across a 350 cm² film surface area. Such a value is indicatedby the data reported in FIG. 1.

Because of the high gas transmission of films made using the novel UHMWPVC resin compound, such films are particularly useful in themanufacture of plastic storage bags for blood and blood components,particularly platelets. The transmission of gases, specifically oxygen,into blood helps to counter-balance changes in pH that tend to occurover time in blood stored in a closed container of blood.

Plastic films of the present invention preferably are manufactured usinga PVC resin having a inherent viscosity in the range of about 1.25 toabout 2.00, most preferably about 1.71. A high inherent viscosity valueimproves the ability of the subject resin to absorb plasticizer; themore plasticizer absorbed by the resin, the higher the gas transmissionof the resulting film. This range of inherent viscosity for the UHMW PVCresins used in manufacturing the novel PVC film can be up to 80% higherthan PVC films currently available, made from PVC compounds withinherent viscosities of 1.06 to 1.10.

Films may be made using the novel PVC UHMW compound by usingconventional methods known and used in the industry. The percentage TOTMused in the PVC resin compositions can exceed the 41% limitation foundin current PVC films, and preferably can be as high as 57% by weightbased on the UHMW resin selected.

The novel films described herein may be formed into containers or othermedical products, such as tubing, because they are capable of beingsealed. Sealing methods that may be used in forming the novel film intoproducts include heat, radio-frequency (RF), ultra-sonic, and chemical,among others.

Flexible plastic containers can be made from the film described hereinusing conventional manufacturing techniques known and used in theindustry. The film is manufactured from a UHMW PVC resin having aninherent viscosity of about 1.25 or greater, preferably about 1.50 to1.80, and most preferably about 1.71, and plasticized with about 53%TOTM plasticizer. In addition, conventionally used stabilization systemsalso may be added to the film PVC composition, as needed. The preferredwall thickness of blood bags manufactured using the novel PVC film maybe of a conventional range of about 0.005 to about 0.025 inch,preferably about 0.012 to 0.018 inch, with 0.015 inch being the mostpreferred. This wall thickness results in containers having sufficienttensile strength to withstand conventional use in the collection andprocessing of blood and blood components. Typically, films of theplasticized PVC having the above thicknesses simply are edge sealed withappropriate fittings or are sealed using RF sealing methods.

In one embodiment, blood bags manufactured from the novel PVC film areincorporated into a multiple blood bag system, which includes varioushardware, valving systems and connecting means that provide what isknown as a "closed system".

As used herein, the term "closed" in reference to blood bags or bloodbag systems refers to a system of multiple blood bags connected understerile conditions via tubing and including valve devices as required topermit blood collected into one bag to be transferred into another bagwithout exposure to the environment outside the system. A typical"closed" system is described in U.S. Pat. No. 4,586,928 to Barnes et al.

An example of a multiple blood bag system that may include bags andother components manufactured using the novel PVC film is illustrated inFIG. 2. A multiple blood bag system 10 generally includes a donor bag 12joined to one or more satellite bags 18, by flexible tubing 22 and aY-connector 24. There are two satellite bags, 18a and 18b, in theillustrated example. The donor bag 12 and satellite bags 18 may have oneor more access ports 16 and the donor bag 12 is equipped with a bloodcollection tube 14 leading to a donor needle (not shown).

In the illustrated example, one access port 16a of the donor bag 12 isconnected to an additive solution bag 20. In other configurations, thedonor bag 12 may be connected to other types of bags. Fluid flow throughtubing 22 from bag 12 is controlled by conventional valving meanslocated, for example, within tubing 22. Such multiple blood bag systemsalso may include one or more in-line integral filters 26.

In practicing the illustrated multiple blood bag system, blood may becollected into the donor bag 12 from a donor through the connected donorneedle tubing 14 and then, after being centrifuged to separate the bloodinto desired blood components, such as red blood cells and plasma, theblood components can be processed into other bags for manufacture ofblood products. Such systems 10 typically may include blood bag systemsin which bags or other items (e.g. in-line filters, and the like) are"sterile docked" to other bags or tubing as described, for example inU.S. Pat. No. 4,507,119 to Spencer.

The donor bag 12 as well as satellite bags 18a and 18b and the flexibletubing 22 may be manufactured using the UHMW PVC film disclosed herein.Alternatively, any flexible polymer, such as polyethylene, may be usedto manufacture the tubing.

The UHMW PVC film of the present invention may be used to manufactureblood bags and other components used in a multiple blood bag system,including flexible tubing. Additional examples of systems includingin-line filters can be found in U.S. Pat. No. 4,596,657 to Wisdom, or inU.S. Pat. Nos. 4,810,378 and 5,089,146 to Carmen et al. The presence ofin-line filters 26 as part of a multiple blood bag system 10 makes itpossible to assure the removal of deleterious white blood cells fromblood components, such as red blood cells, before the cells are storedfor prolonged periods. This can also be done prior to storage of othercomponents, such as platelets, depending on the location of the filterrelative to the rest of the system.

In some multiple blood bag systems 10, a single filter may be usedsimply to filter the red blood cells to free them of white blood cells.In other cases, the system might include both red blood cell filters andplatelet filters. Examples of this type of system can be found in U.S.Pat. No. 5,100,564 to Pall et al.

FIG. 3 illustrates a bag 30 partially cut away to show liquid contents.The bag 30 may be made from the PVC film of this invention that issingle or double edge-sealed 32a, 32b (as illustrated) and includesvarious tubing 34 and ports 36a, 36b. The tubing 34 may include anin-line filter (not shown) and may be connected to other bags (notshown) into which the contents of the main bag 30 can be expressed aftermanipulation using various valves 38a, 38b as shown.

Although in a preferred embodiment of the present invention, the PVCfilm is described as being manufactured into plastic containers forcollecting, processing, and/or storing blood and blood components, thefilm also may be used in the manufacture of a variety of other medicalproducts such as tubing.

EXAMPLES

Preferred UHMW PVC resins are available from Occidental Chemical Corp.,Vinyls Divisions, Dallas, Tex. under the trademarks OXY 280™, OXY 300™,OXY 320™ and OXY 410™. The TOTM plasticizer was obtained from Nuodex,Huls America, Inc., Pistcatoway, N.J. The PVC film of this example wasmade using conventional stabilization systems well known to thoseskilled in the art. (See, for example, the Warner et al. patent.) Theamount of TOTM used in the following illustrative example formulationwas calculated on a weight-percentage basis.

A preferred formulation for a UHMW PVC resin compound embodying thepresent invention is found in the following Table II:

                  TABLE II                                                        ______________________________________                                        PVC Resin - UHMW      100 phr                                                 TOTM Plasticizer      120 phr (53%)                                           Epoxized Oil          5 phr                                                   Calcium-Zinc Stabilizer                                                                             0.32 phr                                                Mineral Oil           0.2 phr                                                 ______________________________________                                    

Values in Table II for the components are given in the industrystandard, parts per hundred resin (phr), i.e, parts component with 100parts resin.

As shown in Table III below, film manufactured in accordance with theabove UHMW PVC resin compound formulation results in oxygen transmissionrates that are over twice that attainable from currently commerciallyavailable TOTM plasticized PVC blood bags. In Table III, the oxygentransmission rate for film manufactured using the novel PVC/TOTM plasticis compared with a citrate ester plasticized PVC. Some of this data isshown in bar graph form in FIG. 1.

                  TABLE III                                                       ______________________________________                                        Oxygen Transmission Rates of PVC in 350 cm.sup.2 Films 0.15 mil thick                          Oxygen Transmission Rate                                                      (μmoles/hr) in room air @ 22° C.                   Current TOTM plasticized                                                                       12.9                                                         PVC bags                                                                      TOTM plasticized PVC bags                                                                      27.8                                                         of this invention                                                             Citrate ester plasticized PC                                                                   26.2                                                         bags (e.g., EP 0,138,147)                                                     ______________________________________                                    

A bag manufactured from UHMW PVC film in accordance with the presentinvention is compared with conventional bags for amount of extractioninto blood components stored after seven days. Table IV sets out theresults of measuring the level of extraction over time of TOTMplasticizer into human plasma stored in a one liter blood bagmanufactured from film of the UHMW PVC resin compound according to thepresent invention and having the formula found in Table I above.

                  TABLE IV                                                        ______________________________________                                        One liter bag (41% TOTM control)                                                                One liter bag (53% TOTM)                                    Sample ID                                                                             Day 0    Day 7    Sample ID                                                                             Day 0  Day 7                                ______________________________________                                        P101394A4                                                                             0.4 ppm  0.9 ppm  P101394A                                                                              0.6 ppm                                                                              1.3 ppm                              P101394A5                                                                             0.5 ppm  1.0 ppm  P101394A                                                                              0.7 ppm                                                                              1.6 ppm                              P101394A6                                                                             0.5 ppm  1.0 ppm  P101394A                                                                              0.7 ppm                                                                              1.9 ppm                              P101394B4                                                                             0.6 ppm  0.8 ppm  P101394B                                                                              0.5 ppm                                                                              1.4 ppm                              P101394B5                                                                             0.5 ppm  1.0 ppm  P101394B                                                                              0.6 ppm                                                                              1.9 ppm                              P101394B6                                                                             0.7 ppm  0.9 ppm  P101394B                                                                              0.6 ppm                                                                              5.1 ppm                              MEAN    0.5 ppm  0.9 ppm  MEAN    0.6 ppm                                                                              2.2 ppm                              SD      0.1 ppm  0.1 ppm  SD      0.1 ppm                                                                              1.4 ppm                                                                P = .223                                                                             P = .084                             ______________________________________                                    

After day seven, the mean extraction in parts per million is about 2.2for bags made in accordance with this invention. In contrast, similarPVC bags plasticized with 27 wt % of DEHP or 38 wt % of BTHC extracted430 ppm and 380 ppm after seven days, respectively.

Given the present disclosure, it is believed that numerous variationswill occur to those skilled in the art. Accordingly it is intended thatthe above example be considered illustrative only and in no way limitingand that the scope of the invention disclosed herein should be limitedonly by the following claims.

We claim:
 1. A flexible container for containing blood or bloodcomponents, comprising a polyvinyl chloride (PVC) film manufactured froma polyvinyl chloride compound, said compound comprising:an ultra highmolecular weight polyvinyl chloride resin having an inherent viscosityranging from about 1.25 to about 2.00, as measured by ASTM D-1243; andabout 43 to about 57 weight percent of a plasticizer.
 2. The flexiblecontainer of claim 1, wherein said PVC film has a 22° C. room air oxygentransmission greater than about 18 μmoles O₂ hr/350 cm² film surfacearea.
 3. A multiple blood bag system, comprising at least one saidflexible container of claim
 1. 4. The flexible container of claim 1,wherein said inherent viscosity is from about 1.50 to about 2.00.
 5. Theflexible container of claim 1, wherein the compound includes about 53 toabout 57 weight percent of the plasticizer.
 6. The flexible container ofclaim 4, wherein the compound includes about 53 to about 57 weightpercent of the plasticizer.
 7. The flexible container of claim 1,wherein the plasticizer is one from the group of plasticizers consistingof: tri (2-ethylhexyl) trimellitate; di-(2-ethylhexyl) phthalate; acetyltri-n-butyl citrate; n-butyryl tri-n-hexyl citrate; acetyl tri-n-octylcitrate; and acetyl tri-n-decyl citrate.
 8. The flexible container ofclaim 1, wherein the plasticizer comprises tri (2-ethylhexyl)trimellitate (TOTM).
 9. The flexible container of claim 6, wherein theplasticizer comprises tri (2-ethylhexyl) trimellitate (TOTM).
 10. Theflexible container of claim 2, wherein the plasticizer comprises tri(2-ethylhexyl) trimellitate (TOTM).
 11. A flexible container comprisinga polyvinyl chloride film manufactured from a polyvinyl chloridecompound, said polyvinyl chloride compound comprising:an ultra highmolecular weight polyvinyl chloride resin having an inherent viscosityof at least about 1.25, as measured by ASTM D-1243; and about 43 toabout 57 weight percent of a plasticizer.
 12. The container of claim 11,wherein the plasticizer comprises tri (2-ethylhexyl) trimellitate(TOTM).
 13. The container of claim 11, wherein the inherent viscosity isat least about 1.50.
 14. The container of claim 11 wherein said PVC filmhas a 22° C. room air oxygen transmission greater than about 18 μmolesO₂ /hr/350 cm² film surface area.
 15. The container of claim 11 whereinthe plasticizer comprises di-(2-ethylhexyl) phthalate.
 16. The containerof claim 11 wherein the plasticizer comprises n-butyryl tri-n-hexylcitrate.
 17. A method of processing blood or blood componentscomprising:passing blood or blood components into a flexible containercomprising a polyvinyl chloride film manufactured from a polyvinylchloride compound, said polyvinyl chloride compound comprising an ultrahigh molecular weight polyvinyl chloride resin having an inherentviscosity of at least about 1.25, as measured by ASTM D-1243; and about43 to about 57 weight percent of a plasticizer.
 18. The method of claim17, including storing platelets in the flexible container.
 19. Themethod of claim 17, including storing the blood or blood components inthe flexible container.
 20. The method of claim 17 wherein said PVC filmhas a 22° C. room air oxygen transmission greater than about 18 μmolesO₂ /hr/350 cm² film surface area.